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Diffstat (limited to 'Documentation/parisc/debugging')
| -rw-r--r-- | Documentation/parisc/debugging | 39 |
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diff --git a/Documentation/parisc/debugging b/Documentation/parisc/debugging deleted file mode 100644 index 7d75223fa18d..000000000000 --- a/Documentation/parisc/debugging +++ /dev/null @@ -1,39 +0,0 @@ -okay, here are some hints for debugging the lower-level parts of -linux/parisc. - - -1. Absolute addresses - -A lot of the assembly code currently runs in real mode, which means -absolute addresses are used instead of virtual addresses as in the -rest of the kernel. To translate an absolute address to a virtual -address you can lookup in System.map, add __PAGE_OFFSET (0x10000000 -currently). - - -2. HPMCs - -When real-mode code tries to access non-existent memory, you'll get -an HPMC instead of a kernel oops. To debug an HPMC, try to find -the System Responder/Requestor addresses. The System Requestor -address should match (one of the) processor HPAs (high addresses in -the I/O range); the System Responder address is the address real-mode -code tried to access. - -Typical values for the System Responder address are addresses larger -than __PAGE_OFFSET (0x10000000) which mean a virtual address didn't -get translated to a physical address before real-mode code tried to -access it. - - -3. Q bit fun - -Certain, very critical code has to clear the Q bit in the PSW. What -happens when the Q bit is cleared is the CPU does not update the -registers interruption handlers read to find out where the machine -was interrupted - so if you get an interruption between the instruction -that clears the Q bit and the RFI that sets it again you don't know -where exactly it happened. If you're lucky the IAOQ will point to the -instruction that cleared the Q bit, if you're not it points anywhere -at all. Usually Q bit problems will show themselves in unexplainable -system hangs or running off the end of physical memory. |